Cable connection apparatus

ABSTRACT

Apparatus for the connection of cables comprises a container into which cables are inserted and a number of nested, hollow-walled cylindrical drums are disposed concentrically relative to a central axis. Each drum is displaceable along the central axis between a first position inside the container and a second position protruding outside the container. Each drum, around its outside circumference, has access apertures behind which connection means have been located, which in the second position are accessible for the connection of inserted cables. Excess cable lengths required for displacement lie wound in hollow-walled spaces of the drums. Drum displacements are preferably accomplished by specific rotations in a direction opposed to the winding direction of the excess cable lengths.

BACKGROUND OF THE INVENTION

The present invention is in the field of connecting cables. More inparticular it relates to an apparatus for connecting, possiblyunderground, cables such as copper cables or fibre-optic cables.Apparatus of such a kind are known, for example from references [1] and[2] (for more bibliographic details with regard to the references, seebelow under C. References). Such apparatus comprises a container buriedin the ground which is provided with a cover to close off the top andwith passages in or near a base for cables which can be and/or areconnected in the container. The container is furthermore completelycovered at street level with a cover plate. In the interior of thecontainer is disposed a holder for the connection means such as splicingcassettes for optical fibres or other connector elements to which theconductors of the cables are or can be connected. According to [1], theholder in the container is attached to a withdrawal member by which theholder with the connector elements can be pulled vertically upwards,thus making it accessible above ground for connection work. The excesslength of the various cables required for this purpose lies woundloosely as a helix around the holder in the container. According to [2],the holder is in the form of a sort of cable sleeve which is suspendedvertically in the container or is attached to a withdrawal member, andinto the top of which the cable or cables are sealably inserted. Bymeans of a handle, the cable sleeve can be withdrawn from the containerand raised above ground, whereby in this implementation as well therequired excess length of the various cables lies wound loosely as ahelix around the holder in the container. Such known forms of theapparatus have the drawback that as the number of cables to be connectedincreases, particularly in the case of different network operators, theybecome impracticable and inconveniently arranged (reference [1]), orunusable (reference [2]). Moreover, both devices require relativelylarge reserves of cable, which means that the container cannot be verycompact.

Further from reference [3] an apparatus is known, which comprises anassembly of an inner member and an outer member, which are extensibleand retractable, for bringing outside and hiding again of an electricalwall socket provided in an outer wall of the inner member. The membersare situated cylindrically and concentrically. The cabling of the supplycable for the wall socket, which is introduced into the apparatus fromthe exterior via an inlet in the outer member, has been arranged in theinterior of the apparatus in such a way that the supply cable isconnected and interrupted upon extension and retraction of the innermember, respectively. Such an interruption principle has the advantagethat the required excess length of the introduced cables in the interiorof the apparatus may be limited to minimum. An application for anapparatus, in which the cables should be able to be and to stayconnected during a retracted state, is by no means possible.

SUMMARY OF THE INVENTION

An object of the invention is, amongst other things, to provide anapparatus of the kind described above which overcomes the aforementioneddrawbacks of the known devices.

According to a first aspect of the invention the apparatus comprises acontainer provided with at least one inlet for introducing of cablesinto the container. In the container is situated a cylindrical drum,which is displaceable in a direction parallel to a central axis betweena first position in the interior of the container and a second position,in which the drum projects at least partially outside the container. Thedrum contains connection means for connecting conductors of one or morecables. A cylindrical outer wall of the drum is provided with an accessaperture for access to the connection means in said second position ofthe drum. The drum is double-walled with an inner wall and thecylindrical outer wall, which walls are arranged concentrically relativeto the central axis, and the connection means are located in the hollowinterspace between the inner and outer wall of the drum. Cablesterminated on the connection means run from the at least one inletthrough the hollow interspace to the connection means.

The principle of the cylindrical, hollow-walled construction of the drummakes it possible for, depending on the circumference of the drum, anumber of cables to be terminated around the inside of the drum,which—when the drum is brought outside—become accessible for makingand/or changing (dis)connections. Furthermore, this principle allows theapparatus to be simply expanded by the addition of more drums, which arearranged concentrically, in nested positions relative to one another inthe container, and which can be placed, separately or together, inpositions projecting outside the container. According to a furtheraspect of the invention the apparatus comprises at least one furthercylindrical drum, similar to and in a nested position relative to thefirst called drum. The drums are relative to one another and to thecontainer displaceable in the direction of the central axis between afirst position in which the drums are situated in the interior of thecontainer, and a second position. In the second position at least one ofthe drums projects at least partially outside the container and theconnections means of the at least one drum are accessible via the accessapertures.

To enable a drum to be brought outside the container, extra cablelength, hereafter referred to as excess cable length, is needed, whichcan in principle, if the dimensions of the container and the drums aresuitably chosen, be stored in the container beneath the drums. As thenumber of cables increases, however, this rapidly becomes impracticable.

According to another aspect of the invention, in order to increase thepracticability, the apparatus has been arranged such that excess cablelength of cables terminated on the connection means of the drum havebeen contained at least partially in the hollow interspace between theinner- and outerwalls of the drum concerned, when the drum is in thefirst position. By virtue of this measure, already a better cablearrangement can be realised inside the container.

According to yet another aspect of the invention the apparatus togetherwith the drum or drums contained in the container has been arranged suchthat, in a first position of a drum, at least part of the excess cablelength of the cables lies wound around the cylindrical inner wall of therespective drum. Further guide means are provided which have beenarranged such that the displacement of a drum directed substantiallyalong the central axis is combined with a rotation about the centralaxis. The rotation has a direction which is opposed to the windingdirection of the excess cable length during displacement of a drum fromthe first position to the second or third position. These measures limitthe excess length and prevent undesired torsions in the cables duringdisplacements of a drum. The latter is a particularly importantconsideration in the case of optical cables.

The invention provides a compact apparatus for the connection of cables,the principle of which is applicable to a diverse number of cables andin a wide variety of environments, such as in the ground outsidebuildings or in the floors, walls or ceilings within buildings.Depending on its application the container and the drums of theapparatus may be manufactured of stainless steel or other suitablemetal, or/and of any suitable synthetic materials.

References

-   [1] Germany DE-C-4140701;-   [2] Great Gritain GB-A-2277812;-   [3] U.S. Pat. No. 3,794,956.

The references [1],-,[3] have been incorporated by reference in thepresent application.

BRIEF DESCRIPTION OF THE DRAWING

The invention will now be described in more detail by means of adescription of an embodiment, with reference to a drawing whichcomprises the following figures:

FIG. 1 shows schematically an apparatus according to the invention in afirst state;

FIG. 2 shows schematically the apparatus of FIG. 1 in a second state;

FIG. 3 shows schematically in a vertical cross section an apparatusaccording to the invention in greater detail, in a state correspondingwith FIG. 1;

FIG. 4 shows schematically a horizontal cross section according to theline A—A of the apparatus of FIG. 3;

FIG. 5 shows schematically a horizontal cross section according to theline B—B of the apparatus of FIG. 3;

FIG. 6 shows schematically in a vertical cross section the apparatus ofFIG. 3, in a state corresponding with FIG. 2;

FIG. 7 shows schematically in a cross section a detail of a drum of theapparatus according to FIGS. 3 and 6;

FIG. 8 shows schematically in a spatial view another detail of a drum ofthe apparatus according to FIGS. 3 and 6;

FIG. 9 shows schematically in a vertical cross section a variant of theapparatus;

FIG. 10 shows in a cross section yet another detail of a drum of theapparatus according to FIG. 9;

FIG. 11 shows schematically a cylindrical surface rolled out to form aflat surface in illustration of a specific path for the movementundergone by a drum in a preferred embodiment of the apparatus duringdisplacement;

FIG. 12 shows, in an analogous manner as FIG. 12, a cylindrical surfacerolled out to form a flat surface in order to determine the amount ofexcess length of cable or tube required for the displacement of a drum.

DESCRIPTION OF AN EMBODIMENT

FIG. 1 and FIG. 2 show schematically an apparatus according to theinvention in a first and a second state respectively. The figures show acylindrical container 1 and concentrically therewith a number of, in thepresent example two, hollow, cylindrical drums 2 and 3, such that a drumwith a smaller diameter, here drum 3, is located inside a drum with alarger diameter, here drum 2. In the first state the drums 2 and 3 arein nested positions, inside the container 1. In the present embodimentthe container is positioned underground, i.e. buried, built in orotherwise installed. For the sake of simplicity, “underground” willhereafter be understood to mean, unless stated otherwise, a position orpositioning beneath every form of ground level, floor level or streetlevel 4, whether in the open field, in built-up areas or in buildings,while “above ground” indicates a position or positioning above such alevel. A top 5 of the container extends, at least approximately, to thelevel 4. Underground, one or more cables 6 are introduced into thecontainer. In the interior of each of the drums are arranged connectionmeans (see FIG. 3 et seq.), such as connector panels, on which thecables 6 introduced inside are terminated. Each of the drums is providedon the outside with access apertures 7, optionally sealable by a flap ordoor, behind which apertures the connection means are positioned in thehollow interior of the drum in question. The drums 2 and 3 areincorporated in the container 1 such that by exerting a pulling orpushing force with the aid of suitably positioned pulling or pushingmeans (not drawn), outside or inside the container respectively,according to arrow P₁ in a substantially vertical direction, on one ofthe drums, preferably the middle one, here drum 3, these drums are as itwere telescopically extensible and can in this way be displaced to anabove-ground position. This is the state of the apparatus shown in FIG.2. For telescopic extensibility, it is not necessary for the drums to becylindrical. Instead of a cylindrical outer wall, the drums can beconstructed with one or more flat side walls substantially parallel tothe direction of displacement, which side walls are provided with theaccess apertures. A cylindrical outer wall, however, eases rotation ofthe drums around the central axis, which preferably accompaniesdisplacements of the drums, as will be described hereafter. Suchrotations are indicated in FIG. 2 by arrows P₂ and P₃. The apparatus canalso adopt other states, such as those in which only the drum 2 or thedrum 3 is extended to an above-ground position. In an above-groundposition, such a drum with its access apertures 7 is accessible for workon the connection means mounted behind the apertures. After the work hasbeen performed, the drums can, depending on the chosen pulling orpushing means, be pushed or pulled, or alternatively allowed to fallback under their own weight, to their original underground position.

It is pointed out that, depending on the desired working height, thecontainer can of course also be positioned partly above ground. It isfurthermore pointed out that the application of the apparatus is notlimited to situations with a horizontal level 4. Situations are inprinciple also possible in which the level 4 is slanting or makes aright angle with the horizontal, such as for example if the apparatus isbuilt into a wall of an above-ground or underground space, or is evenpositioned upside down, as would be the case if the apparatus is builtinto a ceiling of such a space.

An embodiment of the apparatus will now be described in more detail inan application for the connection of underground cables, wherein theconnection means used for making or changing (dis)connections can bebrought above ground. To this end, FIG. 3 and FIG. 6 show schematicallya vertical cross section of the apparatus in states corresponding withFIG. 1 and FIG. 2 respectively, and FIG. 4 and FIG. 5 show schematicallya horizontal cross section of the apparatus according to the lines A—Aand B—B respectively in FIG. 3. The figures show the apparatuscomprising a container 10 buried in the ground below street level 11,within which container a first cylindrical drum 30 and a secondcylindrical drum 50 are disposed concentrically relative to a centralaxis x. In closed state as shown in FIG. 3 the container 10 is closedoff by a cover 12. A cover plate 13 hides the container 10 from view.The container 10 consists of a first compartment 14, in which the drumsare located, and a second compartment 16 separated from the firstcompartment by a dividing wall 15, into which second compartment cables19 are introduced into the container 10 via inlets 17 in a wall 18 ofthe container. The wall 18 has, at least in the second compartment, acylindrical inner wall 18′. The drums 30 and 50 are double-walled hollowcylinders, each with an outer wall 31 and 51 respectively and an innerwall 32 and 52 respectively, between which are hollow interspaces 33 and53, and each with a central hollow space enclosed by the respectiveinner wall 40 and 60 respectively. The hollow interspaces 33 and 53 areclosed off at the top by rings 34 and 54 respectively. The outsidediameters of the rings 34 and 54 correspond with the outside diametersof the outer walls 31 and 51 respectively of the drums, while the insidediameters of the rings are smaller than the diameters of the inner walls32 and 52 of the drums, so that overhanging edges 34′ and 54′ areformed. The top of the container also has such an overhanging annularedge 21 with an inside diameter preferably such that during displacementthe drum 30 with its outer wall 31 can slide smoothly through it and cansimultaneously perform a rotation around the central axis x. In such away, the inside diameter of the ring 34, i.e. of the overhanging edge34′, is preferably such that during displacement the drum 50 with itsouter wall 51 can slide smoothly through it, and simultaneously rotate.The diameter of the ring of the drum with the smallest diameter, herering 54 of drum 50, can optionally be chosen to be zero, in which casethe central hollow space 60 of the drum 50 is closed off at the top. Inthe state in which the drums 30 and 50 are located inside the container,the rings 34 and 35 and the edge 21 preferably lie in the same plane.The hollow interspaces 33 and 53 are open at the bottom with annularopenings 35 and 55. The length/height of the drums is chosen such thatin retracted state, as shown in FIG. 3, the drums rest with the bottomof their respective inner and outer walls on the dividing wall 15, as aresult of which the dividing wall bears against the annular openings 35and 55 and can close off these openings at the bottom. Where thedividing wall 15 bears against the annular openings 35 and 55, it isprovided with passages 20 for the (individual) feeding through of cables19 from the second compartment 16 to the first compartment 14 of thecontainer, directly into the hollow interspaces 33 and 53. Connectionmeans, such as connector panels, 41 in drum 30 and 61 in drum 50, aremounted all around in the hollow interspaces, preferably on the innerwall of the respective drum (as drawn; attachment on the inside of theouter wall is also possible). Each fed-through cable 19 has a suitablychosen excess length which differs according to the drum in which therespective cable is terminated. A cable terminated in the hollowinterspace 33 (53) of drum 30 (50) has an excess length 42 (62) and isfastened at one end 43 (63) by attachment means 44 (64), for example atthe inner wall 32 (52), in the vicinity of, preferably just below (asdrawn), the connection means 41 (61) onto which conductors 45 (65) ofthe respective cable are or can be terminated. The excess cable lengths42 (62) of the fed-through cables 19 lie in the hollow interspace 33(53) wound around the cylindrical inner wall 32 (52) of the drum 30 (50)with the same winding direction. The cylindrical outer walls 31 and 51of the drums 30 and 50 are provided all around their outside withflanged protective edges 36 and 56 respectively. The protective edges 36and 56 on the outer walls have outside diameters which are preferablyonly a little smaller than the inside diameters of the inner walls 18′and 32 in order to promote the sliding displacement of the drums and arelocated at a suitably chosen distance H from the rings 34 and 54respectively. If the drums are moved in a direction parallel to thecentral axis x, the maximum distance (here the height) over which thedrums can be moved is limited by the blocking engagement of theprotective edge 36 with the overhanging edge 21 of the container fordrum 30, and of the protective edge 56 and the overhanging edge 34 ofthe drum for drum 50. The construction of the various parts of thedrums, and in particular of the elements cooperating in the aforesaidblocking engagement, is preferably such that if the drum 50 is displacedover a distance greater than H to a position outside the container bythe exertion of a pulling or pushing force, the drum 50 will also pullthe drum 30 outside the container, which is referred to above astelescopic extensibility. If such telescopic extensibility can also becombined with rotations of the drums about the central axis x in adirection opposed to the winding direction of the excess cable lengthsin the drums, then—at least in principle—the minimum required excesslength of the cables, terminated in a given drum, is equal to the lengthof the maximum displacement distance of that drum, in this case excesslength 42 with length H for each cable in drum 30 and excess length 62with length 2H for each cable in drum 50. With such minimum lengths forthe excess cable lengths 42 and 62 respectively, the cable ends 43 and63 will, when the drums are extended to their maximum, i.e. the state asshown in FIG. 6, extend tautly between the passages 20 in the dividingwall 15 and the attachment means 44 and 64 respectively. Preferably, forreasons to be set out below, the excess lengths will be chosen to besomewhat longer. Since each cable end 43 (63) is attached by attachmentmeans 44 (64) to the inner wall of a respective drum, the rotation of adrum required for the unwinding of the excess cable length can inprinciple be the result of reaction forces in the cable ends which aregenerated during the pulling or pushing forces exercised on therespective drum in order to displace the drum. Preferably, however,guide means are provided, which on the one hand keep the lengths of theexcess cable lengths 42, and 62 within reasonable limits and on theother hand avoid undesired pulling and pushing forces in the cable ends,in particular for fibre-optic cables. Such guide means can beimplemented in various ways, such as for example by means of projections37 and 57 recessed in the protective edges 36 and 56 respectively, whichduring displacement of the drums are forced to follow grooves 22 and 38,which are formed by pairs of parallel ridges 23 and 39 provided on theinner walls 18′ and 32. The number of projections 37 and 57 and thecorresponding number of grooves, in this example four, are preferablydistributed at regular intervals around the central axis, for example inthe form of screw thread. In order to prevent the above-mentionedundesired pulling and pushing forces in the cable ends, the groovesshould follow a specific path (see below).

FIG. 7 shows in a cross section a detail of a drum, here drum 30, at aheight such as to show the connection means mounted in the drum. Aconnector panel 70, also called a patch panel, with a number ofconnectors 71 is mounted inside the hollow interspace 33 by means of amounting bracket 72 against the cylindrical inner wall 32, above theplace at which a cable end 43 with attachment means 44 is attached atthe same inner wall 32. Cable conductors 45 are individually terminatedat the bottom of the panel 70 on the connectors 71. In order to improvethe accessibility of the panel bottom for termination, the panel ispreferably removable or pivotally mounted against the inner wall. At thetop of the panel connections can be made with the aid of so-called patchcords 73 of suitable length, which are provided at both ends withcoupling connectors 74, between connectors on the same connector panel70 or on another similar connector panel 70′ also mounted on the innerwall 32 of the same drum. This is shown in FIG. 8 in a spatial view of adetail of the drum 30. The patch cords can hang loosely in the hollowinterspace, but can also be bundled and fed through a troughing 75provided around the inside of the outer wall 31. By choosing suitableconnectors, either electrical or optical, such connector panels can bedesigned to accommodate conductors of copper cables and fibre-opticcables, thus making the apparatus applicable for a broad spectrum ofenergy and signal transmission cables, not only separately but alsosimultaneously. In the latter case, only connectors of the same type canin principle be connected to one another, unless patch cords or alsoconnectors incorporating electro-optical converters can be employed.Instead of by the use of patch cords, the connections on a connectorpanel or between two connector panels can also be made with the aid offixed wiring, which is connected via switching means controllable by anelectronic switch panel in order to make the desired (dis)connections.

FIG. 9 shows a variant of the apparatus, wherein the container isprovided with cable guide tubes 90, through which the cables 19 to beterminated on the connection means are led from the inlets 17 via thepassages 20 to the respective connection means 45 and 65 in the hollowinterspaces 33 and 53 of the drums 30 and 50 respectively. In a similarway as for the cables 19 in FIG. 3, the guide, tubes 90 with excess tubelengths 91 and 92 lie wound in the hollow interspaces 33 and 53respectively of the drums 30 and 50, while their tube ends 93 and 94 areattached with attachment means 95 and 96 to the respective inner walls32 and 52 of the drums. The minimum lengths of the excess tube lengths91 and 92 correspond with those of the cables. The guide tubes must beflexible and resilient in order not to hinder the unwinding and windingup of the cables in the guide tubes during displacement of the drums. Atthe inlets 17 of the container, the guide tubes 90 are preferablyprovided with tube coupling elements 97 for coupling with external cableguide tubes, so that cables to be terminated in the container are fedfrom an external tube system to the inside, for example with the aid ofthe customary cable blowing techniques.

FIG. 10 shows, in an analogous manner as FIG. 7, how a tube end 101 anda cable end 102 disposed therein are attached with attachment means 103and 104 respectively to the inner wall 32 of drum 30.

The specific path followed by grooves such as grooves 22 and 38 will nowbe explained in more detail with reference to FIG. 11 and FIG. 12. FIG.11 shows schematically a relevant part of a view of a cylindrical innerwall with diameter D, such as the inner wall 186 of the container 10 orthe inner wall 32 of the drum 30, rolled out flat to form a rectangle110 with a height h=H and length l=πD. H corresponds with the maximumheight, or distance, over which one drum, here drum 30, can be movedrelative to the container or drum 50 relative to the drum 30 directlysurrounding it, as shown in FIG. 6. The length l=πD corresponds to thecircumference of the cylindrical inner wall. At equal horizontalintervals of ¼πD are located grooves formed by pairs of ridges 111,corresponding with the above indicated ridges 23 and 39, and grooves 22and 38 on the inner walls 18′ and 32 respectively. The path of such agroove is, seen in the flat surface, an arc c with radius R≧H, which atheight h=0 makes a right angle with the cylinder circumference 112 ofthe inner wall, and at height h=H makes an angle α≧0 with cylindercircumference 113. The projection c′ of the arc c on the cylindercircumference 112 has a length l=φ·D, where φ is the angle in radiansthrough which a drum rotates during displacement out of the containerover a height h=H. For the radius R of the arc, which for a givenmaximum displacement height H per drum is a function of the angle φ andthe diameter D of the inner wall with the grooves, the followingexpression holds: $\begin{matrix}{{R\left( {\varphi,D} \right)} = {\frac{1}{2}{\varphi \cdot D}\left\{ {1 + \left( \frac{H}{\varphi \cdot D} \right)^{2}} \right\}}} & \left\{ 1 \right\}\end{matrix}$And for the angle α:cosα=H/R  {2}.During such a displacement, the projections of the protective edge of adrum, such as projections 37 or 57 on drum 30 or 50 respectively, followsuch arc-shaped grooves, causing the drum to rotate and with it eachrigidly coupled part, such as the attachment means 44 or 64 in the caseof a cable end and 95 or 96 in the case of a tube end, in the drum overthe angle φ. It is pointed out that what is described below for cableends also holds mutatis mutandis for tube ends. If the cable ends lyingin the hollow interspace of a drum are wound with an average diameterD′<D, the minimum length of the excess cable length which is needed forsuch a displacement to assure undisturbed unwinding of the excess cablelength, can be determined from formula [1], with L=R(φ,D′). This isschematically shown in FIG. 12 for two cable ends such as in drum 50.

On the inner walls 32 and 18′ of the drum 30 and the container 18respectively, the grooves are preferably configured such that the pathsof the grooves for the inner wall rolled out flat, as shown in FIG. 11,follow identical arcs c with a projection c′ on the cylindercircumference 92 of the same length. Since the diameters of these innerwalls 32 and 18′, indicated by D₁ and D₂ respectively, differ, however(D₁<D₂), the angles φ₁ and φ₂, over which the drums 30 and 50 rotateduring displacement to h=H also differ, as given by φ₁·D₁=φ₂·D₂. In thehollow interspaces 53 and 33 lie the excess lengths 62 and 42 in theretracted state (FIG. 3) with diameters D₁′<D₁ and D₂′<D₂ respectively.This means that for the displacement of drum 50 relative to thecontainer 18 over a distance H, the excess cable length 62 of each ofthe cables in that drum must in the first instance have a minimum lengthL₁₁=R(φ₁, D₁′), while the cables in drum 30 must have for itsdisplacement over the distance H an excess cable length 42 with aminimum length L₂=R(φ₂,D₂′). For the cable ends in the drum 50, theminimum length L₁₁=R(φ₁,D₁′) is, however, not enough. If the drum 50 ispulled or pushed further out of the container, so that for this drumh>H, drum 30 will also be pulled outside to a maximum distance h=H fordrum 30 and distance h=2H for drum 50. The drum 50 is therefore, as itwere, rigidly coupled to the drum 30 and fully undergoes the rotationover the angle φ₂ of the drum 30. The cable ends in the drum 50therefore need an extra excess cable length with a minimum lengthL₁₂=R(φ₂,D₁′). In total, therefore, each cable end in drum 50 needs tohave an excess cable length with a minimum lengthL₁=L₁₁+L₁₂=R(φ₁,D₁′)+R(φ₂,D₁′).

In principle, the radius R can be chosen to be equal to the distance H,so that the angle α=0. Preferably, however, the angle α>0, for exampleα≧30°, as a result of which the required rotations need little or noextra support during the displacements of the drums to the outside andthen back inside. On the other hand, a greater minimum length is neededfor the excess cable length. A quantitative example will show that forα=30° the length of the required excess cable is still within reasonablelimits:

-   -   H=60 cm and α=30°→R=69.2 cm    -   D₁=66 cm and D₁′=50 cm→φ₁=0.594 rad    -   D₂=96 cm and D₂′=80 cm→φ₂=0.408 rad.        For the minimum length of the excess length of the cables in        drum 50 it is then found: $\begin{matrix}        {L_{1} = {L_{11} + L_{12}}} \\        {= {{R\left( {\varphi_{1},D_{1}^{\prime}} \right)} + {R\left( {\varphi_{2},D_{1}^{\prime}} \right)}}} \\        {= {{75.5 + 98.4} = {173.9\quad{cm}}}}        \end{matrix}$        and for that of the cables in drum 30:        L ₂ =R(φ₂ ,D ₂′)=71.5 cm.        This shows that the calculated L₁ is relatively only a little        greater than one winding (173.9 cm vs πD₁′=157.1 cm), and L₂ is        only a little greater than a quarter of a winding (71.5 vs        ¼πD₂′=62.8 cm).

The above calculation described on the basis of formulae {1} and {2} forthe determination of the “minimum” required length for the excess cablelengths in a drum only holds for the case that the attachment means areprovided at the bottom of the drum near the dividing wall 15, andtherefore offers a theoretical approach. In practice, the attachmentmeans are provided higher in the drums, possibly just beneath theconnector panels, and, as already indicated, preferably a>0 is chosen.Taking this approach as a guide, and applying the thus obtained‘minimum’ lengths for the excess cable, has the advantage that duringeach displacement and in any extended state, in particular for verticalapplication of the apparatus, the cable ends can always hang loosely inthe drums between the attachment means and the passages in the dividingwall. Consequently, the cable guidance for the unwinding and subsequentwinding up of the excess cable lengths during the displacement of thedrums can be further improved by providing hollow-walled cylindricalrings 24 and 25 (shown dotted in the FIGS. 3, 6 and 9) in the container,each consisting of a cylindrical inner and outer wall, concentric withthe central axis x. The ring 24 (25) is attached at the bottom with itsinner and outer wall to the dividing wall 15, and extends, in retractedstate from the drums, with an open top inside the hollow interspace 33(53) of drum 30 (50) up to a height below the attachment means, viz. 44(64) in FIG. 3 and 95 (96) in FIG. 9. In this state the excess lengths,excess cable lengths 42 and 62 in FIG. 3, and excess tube lengths 91 and92 in FIG. 9, lie within the hollow-walled rings 24 and 25. The internalthickness of the hollow-walled rings is greater than the thickness ofthe thickest cable or guide tube employed, and smaller than twice thisthickness, but preferably one and a half times this thickness. Theheight of the hollow-walled rings can differ from one drum to another,for example depending on the minimum excess length determined for adrum.

If the container is suitably dimensioned, additional excess cable lengthcan optionally be held in reserve in the first compartment and/or in thesecond compartment, preferably in the hollow-walled rings.

Depending on the environment of the application, the inlets and/orpassages 17 and 20 are provided with sealing rings to prevent theingress of undesired substances from the environment.

There are various possibilities for achieving the pushing and/or pullingforces required to move the drums to the outside and back inside again,depending on the weight and size of the apparatus. For small andlightweight drums, externally applied manpower may be sufficient. Forlarger and heavier apparatus, however, drawing or hoisting means may beapplied, for example from an engineer's vehicle, which engage on theupper ring of the inner drum. This upper ring can be provided for thispurpose with one or more pulling rings. For the internal pushing-up ofthe drums, use can be made of, for example, an electromechanical orpneumatic lifting jack or telescopically extensible rod mechanismlocated in the central hollow space of the inner drum between thedividing wall of the container and the upper ring of the inner drum.

Since the direction of the effect of gravity on the excess cable length,in case the apparatus is built in ceilings, is reversed with respect tocases in which the apparatus is built in ground or bottom, each drumshould preferably be provided with supporting means, e.g. an annularcross-plate, on which the excess cable length can lie, if the respectivedrum is in retracted state. Such supporting means should be located inthe hollow interspace of the drum near the attachment means 44, 64 or96.

1. Apparatus for the connection of cables the apparatus comprising: acontainer having at least one inlet for the introduction of cables intothe container, a first cylindrical drum displaceable in a directionparallel to a central axis (x) between a first position in the interiorof the container and a second position in which the first drum projectsat least partly outside the container, and connection means, located inthe first drum, for the connection of conductors of at least one of thecables, a cylindrical outer wall of the first drum being provided withone or more access apertures for access to the connection means in saidsecond position, and wherein the first drum is double-walled with aninner wall and the cylindrical outer wall, which walls are arrangedconcentrically relative to the central axis, and that the connectionmeans are located in a hollow interspace between the inner and outerwalls of the first drum, cables terminated on the connection means beingled from the said one inlet via the hollow interspace to the connectionmeans.
 2. The apparatus according to claim 1 wherein the apparatuscomprises at least one further cylindrical drum similar to and in anested position with the first drum, said first and further drums aredisplaceable relative to one another and relative to the container in adirection of the central axis between a first position in which thefirst and further drums lie in the interior of the container and asecond position in which at least one of the first and further drumsprojects at least partly outside the container, with the connectionmeans of said one drum being accessible via said one of the accessapertures.
 3. The apparatus according to claim 2 wherein the first andfurther drums are displaceable relative to one another and relative tothe container in the direction of the central axis between the firstposition and a third position, in which third position a drum of saidfirst and further drums having a smaller cylinder diameter than otherones of the first and further drums projects at least partly outside adrum with a larger cylinder diameter than other ones of the first andfurther drums, and the drum having the larger cylinder diameter projectsoutside the container, with the connection means of both the drum withthe smaller cylinder diameter and the drum with the larger cylinderdiameter being accessible via respective ones of the access apertures.4. The apparatus according to claim 1 wherein excess length of cablesterminated on the connection means of the first drum lies in the hollowinterspace between the inner and outer walls of the first drum when saidfirst drum occupies the first position.
 5. The apparatus according toclaim 4 wherein in the first position of the first drum at least part ofthe excess length of the cables lies wound around the cylindrical innerwall of the first drum, and guide means are provided which have beenarranged such that the displacement of the first drum directedsubstantially along the central axis is combined with a rotation aboutthe central axis, said rotation having a direction which is opposed tothe winding direction of the excess cable length during displacement ofthe first drum from the first position to the second or a thirdposition.
 6. The apparatus according to claim 5 wherein the guide meanshave been arranged such that during the displacement combined with therotation of the first drum, every point on the first drum describes apath which lies in a cylindrical surface around a vertical axis andwhich, if the cylindrical surface is rolled out into a flat surface,corresponds with an arc (c) with a radius (R) which is a function of theangle (φ) and the distance (H) over which the rotation and thedisplacement respectively take place and of the diameter (D) of saidcylindrical surface.
 7. The apparatus according to claim 1 wherein saidfirst drum comprises means for being engaged by external pulling means(P₁) by which at least said first drum can be pulled from the firstposition into the second position.
 8. The apparatus according to claim 1wherein the container comprises two compartments separated from eachother by a dividing wall of which a first compartment encloses the firstdrum and of which the second compartment comprises said one inlet forthe introduction of one or more cables into the second compartment, andthe dividing wall comprises passages for feeding of the one or morecables from the second to the first compartment, which passages arepositioned such that a fed-through cable comes out directly in thehollow interspace of the first drum containing the connection means onwhich the fed-through cable has been terminated.
 9. The apparatusaccording to claim 8 wherein for said first drum the container in thefirst compartment comprises a hollow-walled cylindrical ring, concentricwith the central axis, and attached at one side to the dividing wall andextending with an other, open side into the hollow interspace of saidfirst drum, in such a way that at least in the first position of thefirst drum, the excess lengths of the cables terminated in the firstdrum lie within the hollow-walled ring.
 10. The apparatus according toclaim 1 wherein the container comprises cable guide tubes through whichcables terminated or to be terminated on the connection means are guidedfrom said one inlet to the connection means.
 11. The apparatus accordingto claim 1 wherein the container has been positioned at least partlyunderground with a substantially vertical direction of displacement ofthe first drum, with the second position of the first drum correspondingto an at least partly above-ground position.
 12. The apparatus accordingto claim 2 wherein excess length of cables terminated on the connectionmeans of said one drum lies in the hollow interspace between the innerand outer walls of said one drum when said one drum occupies the firstposition.
 13. The apparatus according to claim 12 wherein in the firstposition of said one drum at least part of the excess length of thecables lies wound around the cylindrical inner wall of said one drum,and guide means are provided which have been arranged such that thedisplacement of said one drum directed substantially along the centralaxis is combined with a rotation about the central axis, said rotationhaving a direction which is opposed to the winding direction of theexcess cable length during displacement of said one drum from the firstposition to the second or a third position.
 14. The apparatus accordingto claim 12 wherein the guide means have been arranged such that duringthe displacement combined with rotation of the first drum, every pointon the first drum describes a path which lies in a cylindrical surfacearound a vertical axis and which, if the cylindrical surface is rolledout into a flat surface, corresponds with an arc (c) with a radius (R)which is a function of the angle (φ) and the distance (H) over which therotation and the displacement respectively take place and of thediameter (D) of said cylindrical surface.
 15. The apparatus according toclaim 3 wherein excess length of cables terminated on the connectionmeans of a drum lies in the hollow interspace between the inner andouter walls of the first drum when said first drum occupies the firstposition.
 16. The apparatus according to claim 15 wherein in the firstposition of the first drum at least part of the excess length of thecables lies wound around the cylindrical inner wall of the first drum,and guide means are provided which have been arranged such that thedisplacement of the first drum directed substantially along the centralaxis is combined with a rotation about the central axis, said rotationhaving a direction which is opposed to the winding direction of theexcess cable length during displacement of the first drum from the firstposition to the second or a third position.
 17. The apparatus accordingto claim 16 wherein the guide means have been arranged such that duringthe displacement combined with rotation of the first drum, every pointon the first drum describes a path which lies in a cylindrical surfacearound a vertical axis and which, if the cylindrical surface is rolledout into a flat surface, corresponds with an arc (c) with a radius (R)which is a function of the angle (φ) and the distance (H) over which therotation and the displacement respectively take place and of thediameter (D) of said cylindrical surface.
 18. The apparatus according toclaim 3 wherein a given one of said first and further drums comprisesmeans for being engaged by external pulling means (P₁) by which saidgiven one drum can be pulled from the first position into the second orthird position.
 19. The apparatus according to claim 2 wherein thecontainer comprises two compartments separated from each other by adividing wall, of which a first compartment encloses the first andfurther drums, and of which the second compartment comprises said oneinlet for the introduction of one or more cables into the secondcompartment, and the dividing wall comprises passages for feeding of theone or more cables from the second to the first compartment, whichpassages are positioned such that a fed-through cable comes out directlyin the hollow interspace of a drum in said first and further drums andcontaining the connection means on which the fed-through cable has beenterminated.
 20. The apparatus according to claim 3 wherein the containercomprises two compartments separated from each other by a dividing wall,of which a first compartment encloses the first and further drums, andof which the second compartment comprises said one inlet for theintroduction of one or more cables into the second compartment, and thedividing wall comprises passages for feeding of the one or more cablesfrom the second to the first compartment, which passages are positionedsuch that a fed-through cable comes out directly in the hollowinterspace of a drum in said first and further drums containing theconnection means on which the fed-through cable has been terminated. 21.The apparatus according to claim 4 wherein the container comprises twocompartments separated from each other by a dividing wall, of which afirst compartment encloses the first and further drums, and of which thesecond compartment comprises said one inlet for the introduction of oneor more cables into the second compartment, and the dividing wallcomprises passages for feeding of the one or more cables from the secondto the first compartment, which passages are positioned such that afed-through cable comes out directly in the hollow interspace of a drumin said first and further drums containing the connection means on whichthe fed-through cable has been terminated.
 22. The apparatus accordingto claim 21 wherein for each one of said first and further drums thecontainer in the first compartment comprises a hollow-walled cylindricalring, concentric with the central axis, and attached at one side to thedividing wall and extending with an other, open side into the hollowinterspace of said each one drum, in such a way that at least in thefirst position of said each one drum, the excess lengths of the cablesterminated in said each one drum lie within the hollow-walled ring. 23.The apparatus according to claim 5 wherein the container comprises twocompartments separated from each other by a dividing wall, of which afirst compartment encloses the first and further drums, and of which thesecond compartment comprises said one inlet for the introduction of oneor more cables into the second compartment, and the dividing wallcomprises passages for the feeding of the one or more cables from thesecond to the first compartment, which passages are positioned such thata fed-through cable comes out directly in the hollow interspace of adrum in said first and further drums containing the connection means onwhich the fed-through cable has been terminated.
 24. The apparatusaccording to claim 23 wherein for each one of said first and furtherdrums the container in the first compartment comprises a hollow-walledcylindrical ring, concentric with the central axis, and attached at oneside to the dividing wall and extending with an other, open side intothe hollow interspace of said each one drum, in such a way that at leastin the first position of said each one drum, the excess lengths of thecables terminated in said each one drum lie within the hollow-walledring.
 25. The apparatus according to claim 6 wherein the containercomprises two compartments separated from each other by a dividing wall,of which a first compartment encloses the first and further drums, andof which the second compartment comprises said one inlet for theintroduction of one or more cables into the second compartment, and thedividing wall comprises passages for feeding of the one or more cablesfrom the second to the first compartment, which passages are positionedsuch that a fed-through cable comes out directly in the hollowinterspace of a drum in said first and further drums containing theconnection means on which the fed-through cable has been terminated. 26.The apparatus according to claim 25, wherein for each one of said firstand further drums the container in the first compartment comprises ahollow-walled cylindrical ring, concentric with the central axis, andattached at one side to the dividing wall and extending with an other,open side into the hollow interspace of said each one drum, in such away that at least in the first position of said each one drum, theexcess lengths of the cables terminated in said each one drum lie withinthe hollow-walled ring.
 27. The apparatus according to claim 2 whereinthe container comprises cable guide tubes through which cablesterminated or to be terminated on the connection means are guided fromsaid one inlet to the connection means.
 28. The apparatus according toclaim 3 wherein the container comprises cable guide tubes through whichcables terminated or to be terminated on the connection means are guidedfrom said one inlet to the connection means.
 29. The apparatus accordingto claim 4 wherein the container comprises cable guide tubes throughwhich cables terminated or to be terminated on the connection means areguided from the said one inlet to the connection means.
 30. Theapparatus according to claim 5 wherein the container comprises cableguide tubes through which cables terminated or to be terminated on theconnection means are guided from said one inlet to the connection means.31. The apparatus according to claim 6 wherein the container comprisescable guide tubes through which cables terminated or to be terminated onthe connection means are guided from said inlet to the connection means.